Corrosion resistant metals and metal compositions

ABSTRACT

A metal article including an at least partially heat treated metal composition, and a method for treating the metal article are provided. The method for treating the metal article may include heating the metal article to a first holding temperature of about 690° C., and holding the metal article at the first holding temperature for at least about 10 hours. The method may also include cooling the metal article from the first holding temperature to a first cooling temperature of about 65° C. or less. The method may further include heating the metal article to a second holding temperature of about 615° C., and holding the metal article at the second holding temperature for at least about 10 hours. The method may also include cooling the metal article from the second holding temperature to a second cooling temperature of about 65° C. or less.

This application claims priority to U.S. Provisional patent applicationhaving Ser. No. 62/074,700, which was filed Nov. 4, 2014. Theaforementioned patent applications are hereby incorporated by referencein their entirety into the present application to the extent consistentwith the present application.

BACKGROUND

Hydrocarbons produced from wellheads (e.g., subsea production wellheads)often contain corrosive gases, such as carbon dioxide (CO₂), hydrogensulfide (H₂S), and chloride gases, that may induce corrosion in metalsutilized in various phases of producing and transporting thehydrocarbons. For example, the corrosive gases associated with thehydrocarbons may often induce uniform corrosion, sulfide stresscracking, and/or stress corrosion cracking in the metals. Accordingly,metals having increased corrosion resistance, such as martensiticstainless steel, may often be utilized in the various phases ofproducing and transporting the hydrocarbons.

As demand for hydrocarbons increases, efforts have focused on methodsfor increasing their production. These efforts may often includeincreasing drilling depths at the wellheads. As the drilling depths atthe wellheads increase, the temperatures and pressures may alsocorrespondingly increase. The increased temperatures and pressures,however, also increase the partial pressure of the corrosive gases,thereby increasing the corrosiveness of the gases contacting the metals.

What is needed, then, are improved metals and metal compositions andmethods for treating the metals and the metal compositions.

SUMMARY

Embodiments of the disclosure may provide a metal composition includingcarbon, magnesium, sulfur, phosphorus, silicon, nickel, chromium,molybdenum, copper, cobalt, tungsten, vanadium, nitrogen, iron, andimpurities. The metal composition may include about 0.03 wt % or less ofthe carbon, about 1.00 wt % or less of the manganese, about 0.015 wt %or less of the sulfur, about 0.03 wt % or less of the phosphorus, about1.00 wt % or less of the silicon, about 3.50 wt % to about 4.50 wt % ofthe nickel, about 11.50 wt % to about 14.00 wt % of the chromium, about0.40 wt % to about 1.00 wt % of the molybdenum, about 0.50 wt % or lessof the copper, about 0.06 wt % or less of the cobalt, about 0.10 wt % orless of the tungsten, about 0.05 wt % or less of the vanadium, about0.02 wt % or less of the nitrogen, and a balance of the iron and theimpurities.

Embodiments of the disclosure may also provide a metal article includingan at least partially heat treated metal composition. Prior to at leastpartially heat treating, the metal composition may include about 0.03 wt% or less of carbon, about 1.00 wt % or less of manganese, about 0.015wt % or less of sulfur, about 0.03 wt % or less of phosphorus, about1.00 wt % or less of silicon, about 3.50 wt % to about 4.50 wt % ofnickel, about 11.50 wt % to about 14.00 wt % of chromium, about 0.40 wt% to about 1.00 wt % of molybdenum, about 0.50 wt % or less of copper,about 0.06 wt % or less of cobalt, about 0.10 wt % or less of tungsten,about 0.05 wt % or less of vanadium, about 0.02 wt % or less ofnitrogen, and a balance of iron and impurities.

Embodiments of the disclosure may further provide a method for treatinga metal article. The method may include heating the metal article to afirst holding temperature of about 690° C. The metal article may includecarbon, manganese, sulfur, phosphorus, silicon, nickel, chromium,molybdenum, copper, cobalt, tungsten, vanadium, and iron. The method mayalso include holding the metal article at the first holding temperaturefor at least about 10 hours. The method may further include cooling themetal article from the first holding temperature to a first coolingtemperature of about 65° C. or less. The method may also include heatingthe metal article to a second holding temperature of about 615° C., andholding the metal article at the second holding temperature for at leastabout 10 hours. The method may further include cooling the metal articlefrom the second holding temperature to a second cooling temperature ofabout 65° C. or less.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying FIGURES. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale. In fact, the dimensions of the variousfeatures may be arbitrarily increased or reduced for clarity ofdiscussion.

The FIGURE illustrates a flowchart of a method for treating a metalarticle, according to one or more embodiments disclosed.

DETAILED DESCRIPTION

It is to be understood that the following disclosure describes severalexemplary embodiments for implementing different features, structures,or functions of the invention. Exemplary embodiments of components,arrangements, and configurations are described below to simplify thepresent disclosure; however, these exemplary embodiments are providedmerely as examples and are not intended to limit the scope of theinvention. Additionally, the present disclosure may repeat referencenumerals and/or letters in the various exemplary embodiments and acrossthe FIGURES provided herein. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various exemplary embodiments and/or configurationsdiscussed in the various FIGURES. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact.Finally, the exemplary embodiments presented below may be combined inany combination of ways, i.e., any element from one exemplary embodimentmay be used in any other exemplary embodiment, without departing fromthe scope of the disclosure.

Additionally, certain terms are used throughout the followingdescription and claims to refer to particular components. As one skilledin the art will appreciate, various entities may refer to the samecomponent by different names, and as such, the naming convention for theelements described herein is not intended to limit the scope of theinvention, unless otherwise specifically defined herein. Further, thenaming convention used herein is not intended to distinguish betweencomponents that differ in name but not function. Further, in thefollowing discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to.” All numericalvalues in this disclosure may be exact or approximate values unlessotherwise specifically stated. Accordingly, various embodiments of thedisclosure may deviate from the numbers, values, and ranges disclosedherein without departing from the intended scope. Furthermore, as it isused in the claims or specification, the term “or” is intended toencompass both exclusive and inclusive cases, i.e., “A or B” is intendedto be synonymous with “at least one of A and B,” unless otherwiseexpressly specified herein.

It has been surprisingly and unexpectedly discovered that combiningcarbon, manganese, sulfur, phosphorus, silicon, nickel, chromium,molybdenum, copper, cobalt, tungsten, vanadium, nitrogen, and ironproduces a metal composition and/or a metal that meets or satisfiesrequirements of one or more NACE standards. For example, the metalcomposition and/or the metal surprisingly and unexpectedly satisfies therequirements of NACE standards for marine/off-shore environments andsour environments. It has further been surprisingly and unexpectedlydiscovered that treating (e.g., heat treating) a metal and/or a metalarticle having the metal composition according to one or more proceduresdisclosed herein provides a metal and/or a metal article that meets orsatisfies allowable limits established by one or more NACE environments.For example, treating the metal and/or the metal article having themetal composition according to one or more of the heat treatmentsdisclosed herein surprisingly and unexpectedly provides a metal and/or ametal article that satisfies the allowable limits established by NACEMR0175, NACE MR0103, and/or NACE TM0177.

Carbon may form carbides with one or components or elements of the metalcomposition and/or the metal. For example, carbon may form carbides withchromium in the metal composition and/or the metal. The formation ofcarbides may increase a strength and/or hardness of the metal. Theformation of carbides may also decrease an amount or concentration ofone or more components or elements of the metal composition and/or themetal. For example, the formation of carbides between carbon andchromium may decrease the amount of chromium in the metal compositionand/or the metal. Carbon may be present in the metal composition and/orthe metal in an amount of about 0.040 wt % or less, about 0.035 wt % orless, about 0.030 wt % or less, about 0.025 wt % or less, about 0.020 wt% or less, about 0.015 wt % or less, or about 0.010 wt % or less. Itshould be appreciated that all numerical values and ranges disclosedherein are approximate valves and ranges, whether “about” is used inconjunction therewith. It should also be appreciated that the term“about,” as used herein, in conjunction with a numeral refers to a valuethat may be +/−5% (inclusive) of that numeral, +/−10% (inclusive) ofthat numeral, or +/−15% (inclusive) of that numeral. It should furtherbe appreciated that when a numerical range is disclosed herein, anynumerical value falling within the range is also specifically disclosed.

Manganese may be a desulfurization agent in the metal composition and/orthe metal. For example, manganese may be a desulfurization agent whenpresent in the metal composition and/or the metal in an amount greaterthan about 0.050 wt % or greater than about 0.10 wt %. The presence ofmanganese in the metal composition and/or the metal may also decreasecorrosion resistance of the metal in environments containing corrosivegases such as CO₂ and/or H₂S. Manganese may be present in the metalcomposition and/or the metal in an amount of about 1.50 wt % or less,about 1.40 wt % or less, about 1.30 wt % or less, about 1.20 wt % orless, about 1.10 wt % or less, about 1.00 wt % or less, about 0.90 wt %or less, about 0.80 wt % or less, or about 0.70 wt % or less.

Sulfur may increase stress corrosion cracking (SCC) and may decreasecorrosion resistance. For example, an excess amount or concentration ofsulfur may decease resistance to initiation and/or propagation ofcorrosion in the metal. Accordingly, in an exemplary embodiment, thepresence of sulfur in the metal composition and/or the metal may becontrolled or varied. For example, the metal composition and/or themetal may have a maximum sulfur concentration of about 0.015 wt %. Inanother example, sulfur may be present in the metal composition and/orthe metal in an amount of about 0.025 wt % or less, about 0.020 wt % orless, about 0.015 wt % or less, about 0.010 wt % or less, or about 0.005wt % or less.

Phosphorus may increase a strength of the metal. In excess, however,phosphorus may also reduce toughness of the metal. Accordingly, thepresence of phosphorus in the metal composition and/or the metal may bevaried. In at least one example, phosphorus may be present in the metalcomposition and/or the metal in an amount of about 0.040 wt % or less,about 0.035 wt % or less, about 0.030 wt % or less, about 0.025 wt % orless, about 0.020 wt % or less, or about 0.015 wt % or less.

Silicon may be a deoxidizer in the metal composition and/or the metal,and may increase a strength of the metal. An excess amount orconcentration of silicon, however, may decrease a resistance to crackingand/or toughness of the metal. Accordingly, an amount of silicon presentin the metal composition and/or the metal may be varied. For example,silicon may be present in the metal composition and/or the metal in anamount of about 1.30 wt % or less, about 1.20 wt % or less, about 1.10wt % or less, about 1.00 wt % or less, about 0.90 wt % or less, about0.80 wt % or less, or about 0.70 wt % or less.

Nickel may increase toughness and/or strength of the metal. For example,the presence of nickel in the metal composition and/or the metal mayincrease toughness of weld zones of the metal. Nickel may also promotethe formation of one or more phases in the metal. For example, thepresence of nickel may promote the formation of a martensite phase, adelta ferrite phase, or the like. The formation of the phases in themetal may be determined, at least in part, by the concentration ofnickel. In at least one example, nickel may be present in an amount fromabout 3.0 wt %, about 3.1 wt %, about 3.2 wt %, about 3.3 wt %, about3.4 wt %, about 3.5 wt %, about 3.6 wt %, about 3.7 wt %, about 3.8 wt%, about 3.9 wt %, or about 4.0 wt % to about 4.1 wt %, about 4.2 wt %,about 4.3 wt %, about 4.4 wt %, about 4.5 wt %, about 4.6 wt %, about4.7 wt %, about 4.8 wt %, about 4.9 wt %, or about 5.0 wt %. In anotherexample, nickel may be present in an amount from about 3.0 wt % to about5.0 wt %, about 3.1 wt % to about 4.9 wt %, about 3.2 wt % to about 4.8wt %, about 3.3 wt % to about 4.7 wt %, about 3.4 wt % to about 4.6 wt%, about 3.5 wt % to about 4.5 wt %, about 3.6 wt % to about 4.4 wt %,about 3.7 wt % to about 4.3 wt %, about 3.8 wt % to about 4.2 wt %, orabout 3.9 wt % to about 4.1 wt %.

Chromium may increase corrosion resistance of the metal. For example,the presence of chromium in the metal composition and/or the metal in anamount of about 10 wt % or greater may increase the corrosion resistanceof the metal in environments containing corrosive gases (e.g., CO₂and/or H₂S). In at least one example, chromium may be present in anamount from about 10.0 wt %, about 10.5 wt %, about 11.0 wt %, about11.5 wt %, about 11.75 wt %, about 12.0 wt %, about 12.25 wt %, or about12.50 wt % to about 12.75 wt %, about 13.0 wt %, about 13.25 wt %, about13.50 wt %, about 13.75 wt %, about 14.0 wt %, about 14.50 wt %, about15.0 wt %, or about 16.0 wt %. In another example, chromium may bepresent in an amount of about 11.0 wt % to about 14.50 wt %, about 11.50wt % to about 14.0 wt %, about 11.75 wt % to about 13.75 wt %, about12.0 wt % to about 13.50 wt %, about 12.25 wt % to about 13.25 wt %, orabout 12.50 wt % to about 13.0 wt %.

Molybdenum may increase corrosion resistance of the metal. Molybdenummay also promote the formation of one or more phases, such as a ferritephase. In at least one example, molybdenum may be present in an amountfrom about 0.20 wt %, about 0.25 wt %, about 0.30 wt %, about 0.35 wt %,about 0.40 wt %, about 0.45 wt %, about 0.50 wt %, about 0.55 wt %,about 0.60 wt %, about 0.65 wt %, or about 0.70 wt % to about 0.75 wt %,about 0.80 wt %, about 0.85 wt %, about 0.90 wt %, about 0.95 wt %,about 1.0 wt %, about 1.05 wt %, about 1.10 wt %, about 1.15 wt %, orabout 1.20 wt %. In at least one example, molybdenum may be present inan amount from about 0.20 wt % or greater, about 0.25 wt % or greater,about 0.30 wt % or greater, about 0.35 wt % or greater, about 0.40 wt %or greater, about 0.45 wt % or greater, about 0.50 wt % or greater,about 0.60 wt % or greater, about 0.65 wt % or greater, or about 0.70 wt% or greater. In at least one example, molybdenum may be present in anamount from about 0.75 wt % or less, about 0.80 wt % or less, about 0.85wt % or less, about 0.90 wt % or less, about 0.95 wt % or less, about1.0 wt % or less, about 1.05 wt % or less, about 1.10 wt % or less,about 1.15 wt % or less, or about 1.20 wt % or less. In another example,molybdenum may be present in an amount of about 0.30 wt % to about 1.10wt %, about 0.35 wt % to about 1.05 wt %, about 0.40 wt % to about 1.00wt %, about 0.45 wt % to about 0.95 wt %, about 0.50 wt % to about 0.90wt %, about 0.55 wt % to about 0.85 wt %, about 0.60 wt % to about 0.80wt %, or about 0.65 wt % to about 0.75 wt %.

Copper may increase a strength and corrosion resistance of the metal.Copper may also decrease a workability (e.g., hot workability) of themetal. For example, an excess amount of copper in the metal compositionand/or the metal may decrease the hot workability of the metal.Accordingly, an amount of copper present in the metal composition and/orthe metal may be varied to control the properties of the metal. In atleast one example, copper may be present in the metal composition and/orthe metal in an amount of about 0.60 wt % or less, about 0.55 wt % orless, about 0.50 wt % or less, about 0.45 wt % or less, about 0.40 wt %or less, about 0.35 wt % or less, or about 0.30 wt % or less.

Cobalt may improve tempering and hardness, and may also decreasetoughness of the metal. In at least one example, cobalt may be presentin the metal composition and/or the metal in an amount of about 0.075 wt% or less, about 0.070 wt % or less, about 0.065 wt % or less, about0.060 wt % or less, about 0.055 wt % or less, about 0.050 wt % or less,about 0.045 wt % or less, about 0.040 wt % or less, about 0.035 wt % orless, or about 0.030 wt % or less.

Tungsten, similar to copper, may increase a strength and corrosionresistance of the metal. Tungsten may also decrease a workability of themetal. For example, an excess amount of tungsten may decrease the hotworkability of the metal. Accordingly, an amount of tungsten present inthe metal composition and/or the metal may be varied to control theproperties of the metal. In at least one example, tungsten may bepresent in the metal composition and/or the metal in an amount of about0.20 wt % or less, about 0.15 wt % or less, about 0.14 wt % or less,about 0.13 wt % or less, about 0.12 wt % or less, about 0.11 wt % orless, about 0.09 wt % or less, about 0.08 wt % or less, about 0.07 wt %or less, about 0.06 wt % or less, or about 0.05 wt % or less.

Vanadium may increase resistance to SCC and/or a strength of the metal.Vanadium may increase resistance to cracking and/or the strength of themetal by promoting the precipitation of one or more elements orcomponents of the metal composition and/or the metal within grains.Vanadium may also increase resistance to cracking and/or the strength ofthe metal by preventing the precipitation of one or more elements of themetal composition and/or the metal at grain boundaries. For example,vanadium may promote uniform precipitation of carbides and nitrideswithin grains of the metal. Vanadium may also increase resistance tostrain age hardening. In at least one example, vanadium may be presentin the metal composition and/or the metal in an amount of about 0.10 wt% or less, about 0.09 wt % or less, about 0.08 wt % or less, about 0.07wt % or less, about 0.06 wt % or less, about 0.05 wt % or less, about0.04 wt % or less, about 0.03 wt % or less, about 0.02 wt % or less, orabout 0.01 wt % or less.

Nitrogen may form compounds with one or more elements or compounds ofthe metal composition and/or the metal. For example, nitrogen may formcompounds with chromium, thereby decreasing an amount of free chromiumin the metal composition and/or the metal. Nitrogen may also promote theformation of one or more phases (e.g., delta ferrite phase) in themetal. Nitrogen may also increase a hardness of the metal. For example,nitrogen may increase the hardness of the metal when present in anamount of about 0.02 wt % or greater. Nitrogen may decrease corrosionresistance, SCC resistance, and toughness of the metal, and may furtherincrease strain age hardening of the metal. For example, tempering themetal having nitrogen in an amount of about 0.02 wt % or greater mayresult in the formation of nitrides, which may decrease corrosionresistance, SCC resistance, and toughness. Accordingly, theconcentration or amount of nitrogen present in the metal compositionand/or the metal may be varied to control the properties of the metal.In at least one example, nitrogen may be present in the metalcomposition and/or the metal in an amount of about 0.020 wt % or less,about 0.019 wt % or less, about 0.018 wt % or less, about 0.017 wt % orless, about 0.016 wt % or less, about 0.015 wt % or less, about 0.014 wt% or less, about 0.013 wt % or less, about 0.012 wt % or less, about0.011 wt % or less, or about 0.010 wt % or less.

A balance or remainder of the metal composition and/or the metal mayinclude or consist essentially of iron and/or one or more impurities(e.g., unavoidable impurities or byproducts). The impurities may resultfrom one or more of the processes of making or producing the metalcomposition and/or the metal. An amount or concentration of theimpurities may be varied so as to not adversely affect one or moreproperties of the metal. For example, the impurities may be present inthe metal composition and/or the metal in an amount of about 0.60 wt %or less, about 0.55 wt % or less, about 0.50 wt % or less, about 0.45 wt% or less, about 0.40 wt % or less, about 0.35 wt % or less, or about0.30 wt % or less.

A respective concentration or amount of each of the elements orcomponents present in the metal composition and/or the metal may bevaried to control one or more properties of the metal. For example, therespective concentrations of carbon, manganese, sulfur, phosphorus,silicon, nickel, chromium, molybdenum, copper, cobalt, tungsten,vanadium, nitrogen, iron, and/or the impurities may be varied to controlcorrosion resistance, the formation of one or more phases (e.g., deltaferrite phases, gamma phases, etc.), hardness, toughness, strength, orthe like, or any combination thereof. In an exemplary embodiment, themetal composition and/or the metal may include about 0.03 wt % or lessof carbon, about 1.00 wt % or less of manganese, about 0.015 wt % orless of sulfur, about 0.03 wt % or less of phosphorus, about 1.00 wt %or less of silicon, about 3.50 wt % to about 4.50 wt % of nickel, about11.50 wt % to about 14.00 wt % of chromium, about 0.40 wt % to about1.00 wt % of molybdenum, about 0.50 wt % or less of copper, about 0.06wt % or less of cobalt, about 0.10 wt % or less of tungsten, about 0.05wt % or less of vanadium, about 0.02 wt % or less of nitrogen, about0.50 wt % or less of the impurities or byproducts, and a balance ofiron.

The metal composition and/or the metal may be made by alloying, mixing,or otherwise combining carbon, manganese, sulfur, phosphorus, silicon,nickel, chromium, molybdenum, copper, cobalt, tungsten, vanadium,nitrogen, and/or iron with one another. Carbon, manganese, sulfur,phosphorus, silicon, nickel, chromium, molybdenum, copper, cobalt,tungsten, vanadium, nitrogen, and/or iron may be combined or alloyedwith one another in any order or sequence. Carbon, manganese, sulfur,phosphorus, silicon, nickel, chromium, molybdenum, copper, cobalt,tungsten, vanadium, nitrogen, and/or iron may be alloyed via any one ormore processes known in the art. For example, carbon, manganese, sulfur,phosphorus, silicon, nickel, chromium, molybdenum, copper, cobalt,tungsten, vanadium, nitrogen, and/or iron may be heated or melted to amolten solution via one or more melting or foundry processes, and themolten solution may be solidified to the metal or a metal article (e.g.,slabs or billets) containing the metal through one or more castingprocesses, molding processes, forging processes, or the like.Illustrative melting processes may include, but are not limited to, aconverter process, a furnace process (e.g., an electric arc furnaceprocess), a blending process, or the like.

The metal article may be any metal component, part, piece, or the like.For example, the metal article may be a metal slab or billet. In anotherexample, the metal article may be a turbomachine or a turbomachinecomponent. Illustrative turbomachines may include, but are not limitedto, single- or multi-stage centrifugal compressors, single- ormulti-stage steam turbines, single- or multi-stage gas turbines, single-or multi-stage expanders, single- or multi-stage reciprocatingcompressors, rotating separators, supersonic compressors, pumps, gasengines, diesel engines, or the like. Illustrative turbomachinecomponents may include, but are not limited to, impellers, blades,vanes, casings, diaphragms, stators, mechanical fasteners, bearings,heads, pistons, cylinders, rods, shafts, rotary shafts, sleeves, balancepistons, cross-heads, piston rods, connecting rods, crankcases, engineblocks, turbine discs, shroud rings, nose cones, inlet cases, exhaustcases, intermediate casings, valve blocks, nozzle blocks, inlet nozzles,discharge or outlet nozzles, inlet walls, division walls, dischargewalls, labyrinth seals, or the like.

The metal article and/or the metal thereof may be treated to controland/or adjust one or more properties of the metal article and/or themetal thereof. For example, the metal article and/or the metal may besubjected to one or more heat treatments to control and/or adjust one ormore properties (e.g., toughness, strength, hardness, etc.) thereof. Theheat treatments may control a maximum hardness of the metal articleand/or the metal thereof. The heat treatments may include tempering themetal article and/or the metal thereof. For example, the heat treatmentsmay include a first tempering and a second tempering.

The first tempering may include heating the metal article in a furnaceto a holding temperature. The holding temperature may be from about 682°C., about 684° C., about 686° C., or about 688° C. to about 692° C.,about 694° C., about 696° C., or about 698° C. For example, the holdingtemperature may be about 682° C. to about 698° C., about 684° C. toabout 696° C., about 686° C. to about 694° C., about 688° C. to about692° C., or about 697° C. to about 691° C. In an exemplary embodiment,the holding temperature may be about 690° C.

In the first tempering, the metal article may be held at the holdingtemperature for any amount of time or duration. The duration in whichthe metal article may be held at the holding temperature may be at leastpartially determined by a thickness (e.g., maximum thickness) of themetal article. For example, a metal article having a maximum thicknessof about 12.7 cm or less may be held at the holding temperature for aduration of about 9 hours or more, about 9.5 hours or more, about 10hours or more, or about 10.5 hours or more. In another example, a metalarticle having a maximum thickness of about 12.7 cm or less may be heldat the holding temperature for a minimum duration of about 9 hours,about 9.5 hours, about 10 hours, or about 10.5 hours. In anotherexample, a metal article having a maximum thickness of about 12.7 cm orgreater may be held at the holding temperature for a duration of about10 hours or more. In at least one embodiment, the duration in which ametal article having a maximum thickness greater than about 12.7 cm maybe held at the holding temperature may be increased by one hour or onehour increments for each additional 2.54 cm of thickness or fractionthereof greater than or in excess of about 12.7 cm.

In at least one embodiment, the first tempering may include heating themetal article in the furnace from about ambient temperature (e.g., roomtemperature) to the holding temperature. In another embodiment, thefirst tempering may include disposing the metal article in a furnacehaving a temperature between about 205° C. and about 315° C., holdingthe metal article in the furnace at a temperature between about 205° C.and about 315° C. for a predetermined period, and subsequently heatingthe metal article to the holding temperature. The amount of time orduration in which the metal article may be held in the furnace at atemperature between about 205° C. and about 315° C. may be determined,at least in part, by a thickness of the metal article. For example, theduration the metal article may be held in the furnace at a temperaturebetween about 205° C. and about 315° C. may be about one hour for each2.54 cm of thickness, with a minimum duration of about 3 hours.

In the first tempering, the metal article may be heated from aboutambient temperature or from a temperature between about 205° C. andabout 315° C. to the holding temperature at any heating rate. Theheating rate may be determined, at least in part, by a thickness (e.g.,maximum thickness) of the metal article. For example, a metal articlehaving a maximum thickness of about 10.16 cm or less may be heated tothe holding temperature (e.g., about 690° C.) at a heating rate of about225° C. per hour or lower. In another example, a metal article having amaximum thickness of about 10.16 cm or greater may be heated to theholding temperature (e.g., about 690° C.) at a heating rate of about 55°C. per hour or lower.

The first tempering may also include cooling the metal article from theholding temperature to or below a resting or cooling temperature. Thecooling temperature may be from about 55° C., about 60° C., or about 65°C. to about 70° C., about 75° C., about 80° C., or greater. In anotherexample, the cooling temperature may be greater than about 55° C.,greater than about 60° C., greater than about 65° C., greater than about70° C., greater than about 75° C., or greater than about 80° C. Themetal article may be cooled from the holding temperature to or below thecooling temperature in the furnace. An atmosphere of the furnace may becontrolled to prevent or substantially prevent oxidation of the metalarticle and/or the metal thereof during one or more heating and/orcooling processes. For example, the furnace may be filled or purged withan inert gas to reduce or prevent oxidation of the metal article duringthe one or more heating and/or cooling processes.

In the first tempering, the metal article may be cooled from the holdingtemperature to or below the cooling temperature at any cooling rate. Thecooling rate may be determined, at least in part, by a thickness (e.g.,maximum thickness) of the metal article. For example, a metal articlehaving a maximum thickness of about 2.54 cm or less may be cooled fromthe holding temperature to the cooling temperature (e.g., about 65° C.or greater) at a cooling rate of about 275° C. per hour or lower. Inanother example, a metal article having a maximum thickness of about12.7 cm or greater may be cooled from the holding temperature to orbelow the cooling temperature at a cooling rate of about 55° C. perhour. In another example, a metal article having a maximum thicknessbetween about 2.54 cm and about 12.7 cm may be cooled from the holdingtemperature to or below the cooling temperature at a cooling rate ofabout 275° C. per hour divided by the maximum thickness of the metalarticle.

The first tempering may also include cooling the metal article from thecooling temperature to ambient temperature (e.g., room temperature). Aspreviously discussed, the metal article may be cooled from the holdingtemperature to or below the cooling temperature in the furnace where theenvironment may be controlled. In the first tempering, the metal articlemay be cooled from the cooling temperature to ambient temperature (e.g.,room temperature) outside of the furnace in an open environment.

The metal article may be held at ambient temperature for any amount oftime or duration. The duration in which the metal article may be held atambient temperature may be at least partially determined by a thickness(e.g., maximum thickness) of the metal article. For example, a metalarticle having a maximum thickness or about 12.7 cm or less may be heldat ambient temperature for minimum of about 24 hours or less. In anotherexample, a metal article having a maximum thickness of about 12.7 cm orless may be held at ambient temperature for about 36 hours or less,about 32 hours or less, about 28 hours or less, or about 26 hours orless. In another example, a metal article having a maximum thickness ofabout 12.7 cm or greater may be held at the holding temperature for aduration of about 24 hours or greater. In at least one embodiment, theduration in which a metal article having a maximum thickness greaterthan about 12.7 cm may be held at the holding temperature may beincreased by five hours or five hour increments for each additional 2.54cm of the thickness or fraction thereof in excess of about 12.7 cm.

The second tempering may include heating the metal article in a furnaceto a holding temperature. The holding temperature may be from about 607°C., about 608° C., about 610° C., about 612° C., or about 614° C. toabout 616° C., about 618° C., about 620° C., about 622° C., or about623° C. For example, the holding temperature may be about 607° C. toabout 623° C., about 608° C. to about 622° C., about 610° C. to about620° C., about 612° C. to about 618° C., or about 614° C. to about 616°C. In an exemplary embodiment, the holding temperature may be about 615°C.

In the second tempering, the metal article may be held at the holdingtemperature for any amount of time or duration. The duration in whichthe metal article may be held at the holding temperature may be at leastpartially determined by a thickness (e.g., maximum thickness) of themetal article. For example, a metal article having a maximum thicknessof about 12.7 cm or less may be held at the holding temperature for aduration of about 9 hours or more, about 9.5 hours or more, about 10hours or more, or about 10.5 hours or more. In another example, a metalarticle having a maximum thickness of about 12.7 cm or less may be heldat the holding temperature for a minimum duration of about 9 hours,about 9.5 hours, about 10 hours, or about 10.5 hours. In anotherexample, a metal article having a maximum thickness or about 12.7 cm orgreater may be held at the holding temperature for a duration of about10 hours or more. In at least one embodiment, the duration in which ametal article having a maximum thickness greater than about 12.7 cm maybe held at the holding temperature may be increased by one hour or onehour increments for each additional 2.54 cm of thickness or fractionthereof in excess of about 12.7 cm.

In at least one embodiment, the second tempering may include heating themetal article in the furnace from about ambient temperature (e.g., roomtemperature) to the holding temperature. In another embodiment, thesecond tempering may include disposing the metal article in a furnacehaving a temperature between about 205° C. and about 315° C., holdingthe metal article in the furnace at a temperature between about 205° C.and about 315° C. for a predetermined period, and subsequently heatingthe metal article to the holding temperature. The amount of time orduration in which the metal article may be held in the furnace at atemperature between about 205° C. and about 315° C. may be determined,at least in part, by a thickness of the metal article. For example, theduration the metal article may be held in the furnace at a temperaturebetween about 205° C. and about 315° C. may be about one hour for each2.54 cm of thickness, with a minimum duration of about 3 hours.

In the second tempering, the metal article may be heated from aboutambient temperature or from a temperature between about 205° C. andabout 315° C. to the holding temperature at any heating rate. Theheating rate may be determined, at least in part, by a thickness (e.g.,maximum thickness) of the metal article. For example, a metal articlehaving a maximum thickness of about 10.16 cm or less may be heated tothe holding temperature (e.g., about 615° C.) at a heating rate of about225° C. per hour or lower. In another example, a metal article having amaximum thickness of about 10.16 cm or greater may be heated to theholding temperature (e.g., about 615° C.) at a heating rate of about 55°C. per hour or lower.

The second tempering may also include cooling the metal article from theholding temperature to or below a resting or cooling temperature. Thecooling temperature may be from about 55° C., about 60° C., or about 65°C. to about 70° C., about 75° C., about 80° C., or greater. In anotherexample, the cooling temperature may be greater than about 55° C.,greater than about 60° C., greater than about 65° C., greater than about70° C., greater than about 75° C., or greater than about 80° C. Themetal article may be cooled from the holding temperature to or below thecooling temperature in the furnace. As previously discussed, theatmosphere of the furnace may be controlled to prevent or substantiallyprevent oxidation of the metal article during one or more heating and/orcooling processes.

In the second tempering, the metal article may be cooled from theholding temperature to or below the cooling temperature at any coolingrate. The cooling rate may be determined, at least in part, by athickness of the metal article. For example, a metal article having amaximum thickness of about 2.54 cm or less may be cooled from theholding temperature to the cooling temperature (e.g., about 65° C. orgreater) at a cooling rate of about 275° C. per hour or lower. Inanother example, a metal article having a maximum thickness of about12.7 cm or greater may be cooled from the holding temperature to orbelow the cooling temperature at a cooling rate of about 55° C. per houror lower. In another example, a metal article having a maximum thicknessbetween about 2.54 cm and about 12.7 cm may be cooled from the holdingtemperature to or below the cooling temperature at a cooling rate ofabout 275° C. per hour divided by the maximum thickness of the metalarticle.

The second tempering may also include cooling the metal article from thecooling temperature to ambient temperature (e.g., room temperature). Aspreviously discussed, the metal article may be cooled from the holdingtemperature to or below the cooling temperature in the furnace where theenvironment may be controlled. In the second tempering, the metalarticle may be cooled from the cooling temperature to ambienttemperature (e.g., room temperature) outside of the furnace in an openenvironment.

Treating the metal article and/or the metal thereof according to theheat treatments described herein may provide a metal article or a metalthat satisfies or meets allowable limits established by one or more NACEspecific environments, such as NACE MR0175, NACE MR0103, and/or NACETM0177. In at least one embodiment, the metal article and/or the metalthereof may have a hardness greater than, less than, or substantiallyequal to allowable limits established by NACE. For example, treating themetal article and/or the metal thereof according to the first temperingand the second tempering described herein may provide the metal articleand/or the metal thereof with a Rockwell hardness C (HRC) of about 23HRC or greater. In another example, treating the metal article and/orthe metal thereof according to the first tempering and the secondtempering described herein may provide the metal article and/or themetal thereof with a Rockwell hardness C (HRC) of about 23 HRC or less.The metal article and/or the metal thereof may have an HRC less thanabout 23 HRC, less than about 22 HRC, less than about 21 HRC, or lessthan about 20 HRC. In another example, treating the metal article and/orthe metal thereof according to the first tempering and the secondtempering described herein may provide the metal article and/or themetal thereof with a Brinell hardness (HBW) of about 255 HBW or less. Inyet another example, the metal article and/or the metal thereof may havean HBW less than about 255 HBW, less than about 250 HBW, less than about245 HBW, or less than about 240 HBW. In at least one example, treatingthe metal article and/or the metal thereof according to the firsttempering and the second tempering described herein may provide themetal article and/or the metal thereof with a Brinell hardness (HBW) ofabout 255 HBW or greater.

The FIGURE illustrates a flowchart of a method 100 for treating a metalarticle, according to one or more embodiments. The metal article mayinclude carbon, manganese, sulfur, phosphorus, silicon, nickel,chromium, molybdenum, copper, cobalt, tungsten, vanadium, and iron. Themethod 100 may include heating the metal article to a first holdingtemperature of about 690° C., as shown at 102. The method 100 may alsoinclude holding the metal article at the first holding temperature forat least about 10 hours, as shown at 104. The method 100 may furtherinclude cooling the metal article from the first holding temperature toa first cooling temperature of about 65° C. or less, as shown at 106.The method 100 may also include heating the metal article to a secondholding temperature of about 615° C., as shown at 108. The method 100may also include holding the metal article at the second holdingtemperature for at least about 10 hours, as shown at 110. The method 100may further include cooling the metal article from the second holdingtemperature to a second cooling temperature of about 65° C. or less, asshown at 112.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the present disclosure. Thoseskilled in the art should appreciate that they may readily use thepresent disclosure as a basis for designing or modifying other processesand structures for carrying out the same purposes and/or achieving thesame advantages of the embodiments introduced herein. Those skilled inthe art should also realize that such equivalent constructions do notdepart from the spirit and scope of the present disclosure, and thatthey may make various changes, substitutions, and alterations hereinwithout departing from the spirit and scope of the present disclosure.

We claim:
 1. A metal composition, comprising: about 0.03 wt % or less ofcarbon; about 1.00 wt % or less of manganese; about 0.015 wt % or lessof sulfur; about 0.03 wt % or less of phosphorus; about 1.00 wt % orless of silicon; about 3.50 wt % to about 4.50 wt % of nickel; about11.50 wt % to about 14.00 wt % of chromium; about 0.40 wt % to about1.00 wt % of molybdenum; about 0.50 wt % or less of copper; about 0.06wt % or less of cobalt; about 0.10 wt % or less of tungsten; about 0.05wt % or less of vanadium; about 0.02 wt % or less of nitrogen; and abalance of iron and impurities.
 2. The metal composition of claim 1,wherein the metal composition comprises about 0.50 wt % of theimpurities.
 3. The metal composition of claim 1, wherein the metalcomposition comprises about 0.30 wt % of the impurities.
 4. The metalcomposition of claim 1, wherein the metal composition comprises: about0.02 wt % or less of the carbon; about 0.01 wt % or less of the sulfur;about 0.02 wt % or less of the phosphorus; about 0.05 wt % or less ofthe cobalt; and about 0.015 wt % of the nitrogen.
 5. The metalcomposition of claim 1, wherein the metal composition comprises: about0.015 wt % or less of the carbon; about 0.005 wt % or less of thesulfur; about 0.015 wt % or less of the phosphorus; about 0.04 wt % orless of the cobalt; and about 0.01 wt % of the nitrogen.
 6. A metalarticle, comprising: an at least partially heat treated metalcomposition, wherein, prior to at least partially heat treating, themetal composition comprises: about 0.03 wt % or less of carbon; about1.00 wt % or less of manganese; about 0.015 wt % or less of sulfur;about 0.03 wt % or less of phosphorus; about 1.00 wt % or less ofsilicon; about 3.50 wt % to about 4.50 wt % of nickel; about 11.50 wt %to about 14.00 wt % of chromium; about 0.40 wt % to about 1.00 wt % ofmolybdenum; about 0.50 wt % or less of copper; about 0.06 wt % or lessof cobalt; about 0.10 wt % or less of tungsten; about 0.05 wt % or lessof vanadium; about 0.02 wt % or less of nitrogen; and a balance of ironand impurities.
 7. The metal article of claim 6, further comprising aRockwell hardness C of about 23 HRC or greater.
 8. The metal article ofclaim 6, further comprising a Rockwell hardness C of about 20 HRC orgreater.
 9. The metal article of claim 6, further comprising a Brinellhardness of about 255 HBW or greater.
 10. The metal article of claim 6,further comprising a Brinell hardness of about 240 HBW or greater.
 11. Amethod for treating a metal article, the method comprising: heating themetal article to a first holding temperature of about 690° C., whereinthe metal article comprises carbon, manganese, sulfur, phosphorus,silicon, nickel, chromium, molybdenum, copper, cobalt, tungsten,vanadium, and iron; holding the metal article at the first holdingtemperature for at least about 10 hours; cooling the metal article fromthe first holding temperature to a first cooling temperature of about65° C. or less; heating the metal article to a second holdingtemperature of about 615° C.; holding the metal article at the secondholding temperature for at least about 10 hours; and cooling the metalarticle from the second holding temperature to a second coolingtemperature of about 65° C. or less.
 12. The method of claim 11, furthercomprising: cooling the metal article from the first holding temperatureto ambient temperature; and holding the metal article at ambienttemperature for at least about 24 hours.
 13. The method of claim 12,wherein: the metal article has a thickness of about 12.7 cm or greater;and holding the metal article at ambient temperature for at least about24 hours further comprises holding the metal article at ambienttemperature for an additional five hours for each 2.54 cm of thethickness greater than about 12.7 cm.
 14. The method of claim 11,wherein: the metal article has a thickness of about 12.7 cm or greater;and holding the metal article at the first holding temperature for atleast about 10 hours further comprises holding the metal article at thefirst holding temperature for an additional one hour for each 2.54 cm ofthe thickness greater than about 12.7 cm.
 15. The method of claim 11,wherein: the metal article has a thickness of about 12.7 cm or greater;and cooling the metal article from the first holding temperature to thefirst cooling temperature further comprises cooling the metal article ata rate of about 55° C. per hour or lower.
 16. The method of claim 11,wherein: the metal article has a thickness of about 2.54 cm or less; andcooling the metal article from the first holding temperature to thefirst cooling temperature further comprises cooling the metal article ata rate of about 275° C. per hour or lower.
 17. The method of claim 11,wherein: the metal article has a thickness of about 2.54 cm to about12.7 cm; and cooling the metal article from the first holdingtemperature to the first cooling temperature further comprises coolingthe metal article at a rate of about 275° C. per hour divided by thethickness of the metal article or lower.
 18. The method of claim 11,wherein: the metal article has a thickness of about 10.16 cm or greater;and heating the metal article to the first holding temperature furthercomprises heating the metal article at a rate of about 55° C. per houror lower.
 19. The method of claim 11, wherein: the metal article has athickness of about 10.16 cm or less; and heating the metal article tothe first holding temperature further comprises heating the metalarticle at a rate of about 225° C. per hour or lower.
 20. The method ofclaim 11, wherein the metal article comprises: about 0.03 wt % or lessof the carbon; about 1.00 wt % or less of the manganese; about 0.015 wt% or less of the sulfur; about 0.03 wt % or less of the phosphorus;about 1.00 wt % or less of the silicon; about 3.50 wt % to about 4.50 wt% of the nickel; about 11.50 wt % to about 14.00 wt % of the chromium;about 0.40 wt % to about 1.00 wt % of the molybdenum; about 0.50 wt % orless of the copper; about 0.06 wt % or less of the cobalt; about 0.10 wt% or less of the tungsten; about 0.05 wt % or less of the vanadium;about 0.02 wt % or less of the nitrogen; and a balance of the iron andimpurities.